Why is water clear?
For grown-ups: the science
Water looks clear because it barely soaks up light we can see, and it doesn't scatter it around too much either.
Water barely absorbs visible light and doesn't scatter it much as it passes through, which lets light travel straight through and makes water look clear. However, water absorbs red light slightly more than other visible colors, so in deep water like oceans and lakes, where light travels a long way, it can look blue. Water also absorbs infrared and ultraviolet light more easily than visible light.
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Transcript
When you look through a glass of water, you can see right to the other side. Why can water let you see through it like that?
When light hits water, most of it passes right through and keeps going. Water barely soaks up any of that light at all.
Inside water, light doesn't bounce all over the place. So light from things on the other side reaches your eyes nice and clear.
When there's a whole lot of water piled up, a little bit of red light gets soaked in. That's why oceans and lakes can look blue.
Water looks clear because it barely soaks up the light we see, and it doesn't scatter that light around too much.